EP2804730B1 - Method and device for producing a three-dimensional preform in the course of the production of fiber-reinforced molded parts - Google Patents

Description

The invention relates to a method for producing a three-dimensional preform in the course of the production of fiber-reinforced molded parts according to the preamble of patent claim 1, an apparatus for producing a three-dimensional preform in the course of the production of fiber-reinforced molded parts according to the preamble of patent claim 5.

In the course of the production of fiber-reinforced plastic components, also called fiber composite components, the RTM process, resin transfer molding process, is common practice, especially as an industrial use. The entire manufacturing process up to a usable plastic component consists of several subsequent individual processes. In a first process step near-net shape preforms / semifinished fiber products are produced. In this preform process, a plurality of layers of woven or laid fibers, usually in two-dimensional form, are usually stacked or possibly joined (sewing, welding, gluing), so that the fiber-fabric pile already essentially has the necessary outer contours and in some cases already special layers or has layer thicknesses. Preferably, a binder is introduced into the parting lines of the scrim, which after reaching a reshaped three-dimensional shape and its activation and curing to a Fixation of the layers to each other and the draped 3D contour leads. For the preform process, the fabric stacks are then transferred to a forming tool and usually under pressure by closing the forming tool so far approximated the contour of the subsequent molding and cured by activation of the binder (heating and cooling) that the semi-finished fiber near-net shape in a tool of a press Implementation of the RTM process itself can be inserted. Depending on requirements, the semifinished fiber product is still cut or punched at predetermined locations in order to achieve an even more precise contour. After inserting the semi-finished fiber into the tool, the tool halves are closed and injected the necessary resin into the cavity of the tool, wherein the resin impregnates the fiber structure of the semifinished fiber, which includes fibers and firmly binds in the resin matrix. After curing of the resin, the fiber-reinforced plastic component can be removed from the mold. In addition to the RTM process itself, the production of semi-finished fiber already lays the foundation for success in the production of a plastic component. It has been found that the state of the art describes a large number of possibilities for producing a preform, which, however, are usually exhausted in manual or automated production of as flat as possible a fibrous tissue stack, which finally ends up in a press from its 2D form into a 3D Form is transferred. This can be done in a pre-fixed (eg sewn) or even in a flexible state. The aim is to obtain a preform after shaping, which has a sufficient Has inherent rigidity in order to be fully automated and reliable in the tool of a RTM press can be inserted or can be transported and stacked until further use. For producing, forming and fixing the preform, there are a variety of possibilities in the relevant prior art.

In addition to the production by means of RTM, other production processes are also conceivable which can produce fiber-reinforced components from the laying of fiber layers with or without a resin infusion process. In that regard, it would be conceivable to deposit a finite number of precut tissue fibers of predetermined width in different orientations in a draping device and to impregnate the tissue fibers with resin interlayers or to deposit them in prepreg. By means of such laying methods and the subsequent forming in the draping device, it is also possible to produce highly rigid and fiber-reinforced components even without an injection process.

For the so-called draping process and method a variety of different possibilities are known. However, these can basically be subdivided into drapery with one or two rigid mold halves. In general, the female mold is a rigid mold half, either with another rigid mold half or with sequentially movable individual tools (Drapierstempel) successively at least conforming to the contour Forming the fabric layer is merged. The advantage with the latter possibility is that it should be attempted to prevent wrinkling or fiber shifts in the individual layers of the fabric layer. As a result, tensile or thrust movements can be introduced into the fabric layer on areas which are difficult to drape, in order to prevent problems around radii, bends, edges or the like.

document DE 27 01 480 discloses, for example, an apparatus and a method for producing a three-dimensional preform in the course of the production of fiber-reinforced molded parts.

The object of the invention is to specify a method and a device with which, compared with the prior art, in particular two-dimensional, fibrous tissue stacks, three-dimensional preforms can be produced in better and repeatable quality. Next, it should be possible to produce highly complex preforms with a much better precision from a fabric layer, which in particular relates to the fiber orientation and the regularity of the fabric layer used, so that even with complex geometries wrinkling and distortion can be successfully prevented. The semi-finished fiber products obtained by deformation should preferably be able to be used in an RTM process, which is characterized in particular by reproducible process parameters.

The solution of the problem consists for the method according to the characterizing features of claim 1 is that for forming the fabric layer at the contact surface at least a first and subsequently at least a second at least a first and subsequently at least one second Drapierstempel is moved in the draping, wherein the space is bridged with or without overlap to at least one contact surface of a Drapierstempels by means of at least one independently movable or operatively connected to at least one Drapierstempel intermediate holder and that the second Drapierstempel is moved at least partially during the process in the draping in the space between the Drapierstempeln, where it is subsequently or simultaneously moved at an angle or 90 ° to the draping direction such that it forms the fabric layer along the contour and leaves the free space.

The solution of the problem for the device consists according to the features of claim 5 in that an intermediate holder is arranged at least between a first and a second Drapierstempel bridging the space with or without overlap to at least one Drapierstempel, wherein at least one of the Drapierstempel angle to Draping direction is arranged movable.

Advantageously, it is now possible with the method according to the invention and a suitable but also independently usable device adapted to form a preform adapted tissue layers from a substantially planar state (2D) in a complex three-dimensional shape and fix. In particular, it is advantageous that the deformation can be carried out gently and kinks, wrinkles and compressions or distortions of the fabric layer can be avoided during the forming.

• es darf kein unzulässiger Zug auf das Gewebelage gelangen, da sich sonst die Struktur (Faserorientierung und Regelmäßigkeit) verziehen könnte oder die Gewebelage Risse bekommt.
• Es dürfen keine Faltenbildung, Überwerfungen oder Stauchungen beim Drapieren der Gewebelage in Bauteilvertiefungen entstehen.
• Nach Wunsch kann der Fasergewebestapel spannungsarm oder mit einer gezielt definierten Spannung fixiert werden.

In order to improve the transformation of the fabric layer into a cavity shell having cavities, the following points should be noted:

• There must not be any undue tension on the fabric layer, as otherwise the structure (fiber orientation and regularity) could warp or the fabric layer cracks.
• There should be no wrinkling, jolts or buckling when draping the fabric layer in component recesses.
• If desired, the fiber fabric stack can be fixed with low stress or with a specifically defined tension.

In order to further improve the movement behavior of the fabric layer during embedding or during draping into the shell mold, it is also conceivable that on the side of the shell mold at predetermined locations, preferably depressions, friction means or, for example, just foams are arranged. If the fabric layer comes into contact with it, it is clamped there or taken by differentiated stiction with the movement of the Drapierstempels and thereby kept taut or freer. Thus, the following advantages arise with regard to the controllability: Adapted to the forming contour or the mold shell, the draping tools or the draping punches can be controlled in an advantageous and arbitrary sequence. For this purpose, a corresponding mode can be found by means of modern simulation programs, which enables an optimal shift or transformation of 2D layers to a three-dimensional contour.

By the timely retraction of Drapierstempel in the Drapierform with attached intermediate holders, in particular a leading and / or lagging, angularly hired, bent, flexible and / or resilient embodiment, or by the retraction of intermediate holders alone, can folds in the spaces or Joints on the outer edges of the drapery stamps are prevented. In this case, a draping stamp is essentially defined by the fact that it forms a flat three-dimensional partial replica of the draping form that lies opposite it. The intermediate holder is characterized in that it is either carried along a preceding Drapierstempel and at least partially bridges the area between two Drapierstempel and fixes the fabric layer there wrinkle-free. Preferably, the second Drapierstempel will find first parallel with the first Drapierstempel contact with the intermediate holder of the first Drapierstempels and then molding the fabric layer. It is also conceivable that in the course of dipping the second Drapierstempels (by parallel method to the first Drapierstempel) of the second Drapierstempel after contact with the intermediate holder, on this length, is moved substantially transversely to the main movement direction (retraction and extension). Preferably, a resilient, one on a damper and / or arranged on a spring intermediate holder can be used which at least towards the end of the movement (alone or operatively connected to a Drape stamp) in Drapierrichtung in its final position (to replicate the contour of the draping) is pressed.

Preferably, the actuators are designed to process the Drapierstempel as pressure or wegsteubarer linear actuators, such as piston cylinder arrangements or spindle drives.

Further advantageous measures and embodiments of the subject matter of the invention will become apparent from the dependent claims and the following description with the drawing. The device is particularly suitable for carrying out the method, but can also be operated independently without the method.

In particular, it is now possible to arrange at least a first and / or second Drapierstempel an intermediate holder ride along or independently such that the space between the two Drapierstempel is at least partially bridged. Alternatively, the fabric layer in the space between two or more Drapierstempeln (at least partially) can be held down by means of a freely movable or operatively connected to at least one Drapierstempel intermediate holder. In particular, it can be provided that an intermediate holder, preferably at least one Drapierstempel for bridging the free space between two Drapierstempel leading or lagging towards a second moving, but not yet the contour imitating Drapierstempel is arranged.

The following illustrations are not to be regarded as individual case solutions, but also contain general information and task solutions.

Figur 1

Die Nachteile des Standes der Technik bei einer herkömmlichen Drapiervorrichtung in Gegenüberstellung zur

Figur 2

mit Darstellung eines Ausführungsbeispieles des erfindungsgemäßen Verfahrens und einer beispielhaften Vorrichtung, die Verwerfungen oder Überstülpungen in den Freiräumen zwischen zwei Drapierstempeln vermeidet,

Figur 3

ein zweites Ausführungsbeispiel eines Zwischenhalters im Freiraum nach Figur 2,

Figur 4

ein drittes Ausführungsbeispiel zweier Zwischenhalter im Freiraum nach Figur 2,

Figur 5

ein viertes Ausführungsbeispiel zweier Zwischenhalter im Freiraum nach Figur 2,

Figur 6

ein fünftes Ausführungsbeispiel zweier Zwischenhalter im Freiraum nach Figur 2,

Figur 7

ein sechstes Ausführungsbeispiel eines verfahrbaren oder gedämpften Zwischenhalters im Freiraum,

Figur 8

ein siebtes Ausführungsbeispiel eines Zwischenhalters im Freiraum mit einem elastischen Zwischenhalter, welcher zur Oberfläche der Gewebelage konvex gebogen ausgeführt ist und

Figur 9

mit einem beispielhaften Verfahrensablauf unter Verwendung eines quer zur Drapierrichtung verfahrbaren Drapierstempels.

Show it:

FIG. 1

The disadvantages of the prior art in a conventional draping device in contrast to

FIG. 2

depicting an embodiment of the method according to the invention and an exemplary device which avoids distortions or protuberances in the free spaces between two drapery punches,

FIG. 3

A second embodiment of an intermediate holder in the free space after FIG. 2 .

FIG. 4

a third embodiment of two intermediate holder in the free space FIG. 2 .

FIG. 5

a fourth embodiment of two intermediate holder in the free space after FIG. 2 .

FIG. 6

a fifth embodiment of two intermediate holder in the free space after FIG. 2 .

FIG. 7

A sixth embodiment of a movable or damped intermediate holder in the free space,

FIG. 8

a seventh embodiment of an intermediate holder in the free space with an elastic intermediate holder, which is executed convexly curved to the surface of the fabric layer and

FIG. 9

with an exemplary method sequence using a draping punch movable transversely to the draping direction.

To FIG. 1 are the disadvantages of the prior art in a conventional draping device 2 to the effect that with more complex contours of the drape 5, the fabric layer 3 after the process of a first Drapierstempels 4 in the draping direction 9 and subsequent contact with the fabric layer 3 shifts 10 may occur in the fabric layer 3, where no Drapierstempel 4 have been positioned. In the illustrated process within the FIG. 1 From left to right both Drapierstempel 4 in the left drawing are not yet in contact with the fabric layer 3. For draping the fabric layer 3 moves the right Drapierstempel 4 in the middle figure in the draping direction 9 and forms the fabric layer 3 according to the contour of the drape form 5 and pin it down. It can now happen that, due to the entrapment of the fabric layer 3 between the first right-hand draping die 4 and the draping form 5, a displacement 10 occurs within the fabric layer 3 in the region of the next left-hand draping die 4. In particular, the areas in or around the clearance 8 between the drapery punches 4 are susceptible to this action. Moves the second Drapierstempel 4 now in Drapierrichtung 9th it may come to the protuberance or a fold 11, which correspond to a committee criterion.

FIG. 2 now shows the new device according to the invention and the process of the method, in which an intermediate holder 7 is used to bridge the space between the 8 Drapierstempeln 4, which is arranged on a Drapierstempel 4 '. In the following, the reference numeral 4 'for a Drapierstempel 4 is used with operatively connected intermediate holder 7. Preferably, the intermediate holder 7 forms the contour of the draping form 5 in the corresponding area. In the present example, the right-hand Drapierstempel 4 'moves in draping direction 9 and forms the fabric layer 3 according to the contour of the contact surface 12 and the associated contour of the Drapierform 5. The intermediate holder 7 bridges, in particular in the present embodiment, a typical kink of a contour of the drape form 5 and the space 8. The second Drapierstempel 4 left, which is subsequently moved to the first right Drapierstempel 4, reshapes the fabric layer 3 in the further contour, without leave a shift 10 or a fold 11 in the fabric layer 3. It is therefore also not possible that by the method of the second Drapierstempels parts of the fabric layer 3 return to the free space 8. Preferably, in the contact surface 12 of the second Drapierstempels 4 left a recess 14 may be provided, in which the intermediate holder 7 to form a corresponding and uniform total contact surface for the fabric layer 3 remains.

In the FIGS. 3 to 8 are another six possible, but the teaching of the invention not limiting and in particular individual or combinable embodiments for one or more intermediate holder 7 in a free space 8 shown. To FIG. 3 is the intermediate holder 7 a bent in draping 9 metal plate, preferably spring plate, or plastic or other resilient materials. The intermediate holder 7 may be provided with an ani-adhesive layer. Irrespective of this, the intermediate holder 7 can still make contact with the fabric layer 3 before the contact surface 12. As a result of this configuration, warping or displacements are smoothed out before a large-area deformation or draping of the fabric layer 3 takes place through the contact surface 12 of the draping die 4 '. At the same time it is avoided that parts of the fabric layer 3 are moved back into the free space 8 by the last-mentioned deformation. In particular, it is preferred that the (contact) surface of the intermediate holder 7 with the fabric layer 3 is smaller than the contact surface 12 of the actively connected Drapierstempels 4 '. To FIG. 4 is the intermediate holder 7 divided into two parts for the free space 8 and arranged on both the free space 8 forming Drapierstempeln 4 '. Essentially, the contact surface 12 of the intermediate holder 7 is preferably in the connection or transition region in a plane with the contact surface 12 of the Drapierstempels 4 ', but at least after deformation or draping the fabric layer 3, except the contour of the drape form 5 are at this point before deviating contour before. With flexible material of the intermediate holder 7 can after FIG. 5 Be provided that the first contact with the fabric layer 3 receiving intermediate holder 7 is designed bent so that it has starting from the Drapierstempel 4 'less to no contact with the fabric layer 3, wherein an adjacent Drapierstempel 4' mounted second intermediate holder 7 the first intermediate holder 7 bends or straight to a preferably full surface contact with the fabric layer 3, which was carried out in the previous example by the Drapierstempel 4 itself ( FIG. 2 or FIG. 3 ).

In order to obtain a substantially uniform contact in the free space 8, while the second intermediate holder 7 can be arranged spaced from the contact surface 12, as in FIG. 5 represented and exceptionally not flush with the contact surface 12 of the Drapierstempels 4 'be. Alternatively, like FIG. 6 the intermediate holder 7 be made highly flexible. The terms flexible, resilient or flexible are common terms in the art. In order to avoid an ambiguous definition, materials should be chosen that guarantee a recurring flexibility for several production cycles. In this case, the material or the properties of the intermediate holder 7 should be chosen so that it can press the fabric layer 3 strong enough to the contour of the drape form 5 without damaging it. Here is the pressure of pressing and reshaping but (except in targeted exceptional cases) do not damage the material of the fabric layer 3 or within the fabric layer 3 does not lead to shifts / distortions.

With the FIGS. 7 and 8 Further possibilities of an adjustable, flexible, damped or self-movable intermediate holder 7 are shown. This can be done after FIG. 7 the intermediate holder 7 may be supported on a damper 15, an actuator or via a spring and arranged independently or on the second movable Drapierstempel 4 'leading to the contact surface 12.

Depending on the embodiment, provision can be made for the free ends of the intermediate holder 7 and / or the draping stamp edges adjacent to free spaces 8 to be rounded off from the fabric layer 3. The overlap in question by the intermediate holder 7 to the Drapierstempeln 4, 4 'is in almost all Figures (2 . 3, 4, 5, 6, 8 ). A missing overlap can be found in the FIG. 5 (left) and the FIG. 7 ,

To FIG. 8 If possible, a preferred embodiment that the intermediate holder 7, in particular for bridging a free space 8 cross-linear shape of the fabric layer 3 is convexly curved relative to the fabric layer 3, in which case at least one of the Drapierstempel 4, 4 'in the course of its movement in the draping direction 9 the shape of the intermediate holder 7 according to the final contour of the Drapierform 5 transforms. It is of course understandable that after heating and curing of the fabric layer 3 to a preform 6, the Drapierstempel 4, 4 'are moved back into a rest position opposite to Drapierrichtung 9.

In FIG. 9 is still a possible method for draping a fabric layer 3 described with the aid of an intermediate holder 7. For this purpose, at least one of the Drapierstempel 4 not only in draping 9, but also arranged at an angle to it movable.

By way of example, the fabric layer 3 with a draping die 4 is first pressed into a trough of the draping form 5, the intermediate holder 7 preferably further shaping the fabric layer 3 along the contour of the drape form 5 in the direction of a second draping die 4 '. The second Drapierstempel 4 'moves into the deep contour of the Drapierform 5 while a path that at least partially the space 8 between the Drapierstempeln 4 and 4' occupies until shortly before or until he preferably makes contact with the fabric layer 3 or the intermediate holder receives and then moves so that it forms the fabric layer 3 along the contour at an angle or at 90 ° to the draping direction 9 respectively from the free space 8 out. Then, depending on the embodiment, he can still carry out a final shaping in the direction of the draping direction 9 when the second draping die 4 'has passed the intermediate holder 7, in particular an optimum shape contour from the drapery dies 4, 4' and the latter form connecting intermediate holder 7. List of Reference Numerals: P1428 1. 11. fold 2. Draping device 12. contact area 3. fabric layer 13th 4. Drape stamp 14. Return 5. Drape shape 15. Damper 6. preform 7. intermediate holder 8. Freiraum 9. Drape direction 10. shift

Claims (11)

1. Method for producing a three-dimensional preform (6) in the course of the production of fiber-reinforced molded parts, wherein the method is carried out with a draping device (2) comprising at least a draping mold (5) for a woven fabric layer (3) and draping stamps (4, 4') having contact surfaces (12) for reshaping the preform (6) from the woven fabric layer (3) by means of the draping device (2), which draping stamps can be moved relative to the draping mold (5), wherein the draping stamps (4, 4') form at least one clearance (8) with respect to each other, wherein at least one first and subsequently at least one second draping stamp (4, 4') are moved in the draping direction (9) in order to reshape the woven fabric layer (3) on the contact surface (12), wherein with or without overlap with respect to at least one contact surface (12) of a draping stamp (4, 4'), the clearance (8) is bridged by means of at least one independently movable or by means of an intermediate holder (7) that is operatively connected to at least one draping stamp (4, 4'), and
   characterized in that the second draping stamp (4') is moved at least partially during the movement in the draping direction (9) in the clearance (8) between the draping stamps (4 and 4'), wherein it is moved subsequently or simultaneously angularly or at a 90° angle to the draping direction (9) such that it forms the woven fabric layer (3) along the contour and leaves the clearance (8).
2. Method according to claim 1 , characterized in that for bridging the clearance (8) between two draping stamps an intermediate holder (7) is arranged at each draping stamp (4, 4').
3. Method according to one or more of the preceding claims, characterized in that the intermediate holders (7) overlap one another in the clearance (8).
4. Method according to one or more of the preceding claims, characterized in that a spring-elastic intermediate holder (7), an intermediate holder (7) arranged on a damper (15) and/or an intermediate holder (7) arranged on a spring is used, which is pressed into its final position at least towards the end of the movement in the draping direction (9).
5. Device for producing a three-dimensional preform (6) in the course of the production of fiber-reinforced molded parts, wherein the device comprises a draping device (2) having at least one draping mold (5) for a fabric layer (3) and draping stamps (4, 4') which are movable relative to the draping mold (5) for forming the preform (6) from the fabric layer (3) by means of the draping device (2), wherein the draping stamps (4, 4') form at least one clearance (8) with respect to each other, wherein an intermediate holder (7) is arranged at least between a first and a second draping stamp (4, 4'), which bridges the clearance (8) with or without overlap with respect to at least one draping stamp (4, 4'), characterized in that at least one of the draping stamps (4, 4') is movably arranged at an angle to the draping direction (9).
6. Device according to claim 5, characterized in that the intermediate holder (7) is arranged to precede or trail the draping stamp (4, 4') in the draping direction (9).
7. Device according to claim 5, characterized in that the intermediate holder (7) consists of plastic, metal, and/or spring steel sheet.
8. Device according to claim 5, characterized in that the intermediate holder (7) is provided with an anti-adhesive layer.
9. Device according to claim 5, characterized in that the contact surface (12) of a draping stamp (4) is provided at least for partially receiving the intermediate holder (7), in particular with set-back portions (14).
10. Device according to claim 5, characterized in that the intermediate holder (7) forms the associated contour of the draping mold (5).
11. Device according to claim 5 for carrying out the method according to one or more of claims 1 to 4.

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